[SOLVED] Parsing NonEmptyList directly from JSON

Parsing NonEmptyList directly from JSON

Given this JSON: [{"name": "test"}]. Is there a way I can parse this JSON array directly into an Arrow NonEmptyList?

My background is Scala and I'm exploring Ktor + Arrow. I have an endpoint I'd like to do something like: call.receive<NonEmptyList<DataClass>>(). It seems though since serialization is based on an annotation, without a data class with @Serializable it looks like it does not know how to parse the JSON even with @file:UseSerializers(NonEmptyListSerializer::class) on the file.

Solution

After some investigation, with the help of @nomisRev pointers, when using Ktor and installing the JSON serializer, this is what I've arrived at:

install(ContentNegotiation) {
    json(Json {
        serializersModule =
            SerializersModule { contextual(NonEmptyList::class) { args -> NonEmptyListSerializer(args[0]) } }
    })
}

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#contextual-serialization-and-generic-classes

This is being addressed in Arrow: https://github.com/arrow-kt/arrow/pull/3413